Method and apparatus for charging steel slabs into reheating furnace

ABSTRACT

A method and control apparatus for charging steel slabs into the reheating furnace, according to which method and apparatus the volume of pusher stroke necessary for charging a steel slab (SA) is calculated on the basis of the value obtained by the deduction of the sum of the width of the previously charged steel slab (WA) and the prescribed interval between each two slabs in the furnace from the sum of the volume of pusher stroke used for the previously charged steel slab (SB) and the distance on which this slab was transferred after charged (DB), and the value so calculated is transmitted to the pusher driver, thereby making it possible to charge steel slabs into the reheating furnace automatically at constant intervals.

United States Patent [72] lm cntors Osamu Hirata; FOREIGN PATENTS Shillichi'" Maehara- Kiak-wshm Japan 846,466 8/1960 Great Britain 263/6A I311 P 776590 1,503,970 10/1967 France 263/6 [22] Filed Nov. 1,1968 [45] Patented Jan. 19, 1971 Primary Examiner-Charles .l. Myhre [73] Assignee Nippon Steel Corporation Al y Lind & Pollack Tokyo, Japan [54] METHOD AND APPARATUS FOR CHARGING STEEL SLABS INTO REHEATING FURNACE ABSTRACT. A method and control apparatus for charg ng steel slabs into the reheating furnace, according to which 2 Claims, 7 Drawing Figs.

method and apparatus the volume of pusher stroke necessary [52] US. Cl 263/6, f Charging a Steel Slab (SA) is calculated on the basis f the 198/219 value obtained by the deduction of the sum or the width or the [D l Int. Cl F27b 9/14, previously charged Steel Slab (WA) and the prescribed i F27d 3/04 val between each two slabs in the furnace from the sum of the [50] Field of Search 263/6, 6A; volume f pusher ke ed for the previously charged steel 198/219 slab (SB) and the distance on which this slab was transferred R f Ct d after charged (DB), and the value so calculated is transmitted e erences l e to the pusher driver, thereby making it possible to charge steel UNITED STATES PATENTS slabs into the reheating furnace automatically at constant in- 3,450 394 6/1969 Wilde et al 263/6A tervals.

7 i 18 pusher stroke l" detecler i 1? pusher stroke control ler l I 'T 19% Operation width of slclb I controller Sena, 20 I Interval of slob I counter for mwernenl of skid I I l l 13 i i driver for i compleoig ld movable skld l l 12 deteclerfor moving j distance of skid r FIG. 5

r'"' -1 l pusher stroke I detecter l pusher stroke controller manual setter for 9 widthofslab operation controller manual setter for 20 lnterval of slab counter for movement of skid l l3 I detecter for driver f com lete I movemeettof skld movable Skld l I l, 12 l detecter for moving distance of skid OSAMU IIIRATA and SHINICIIIRO MAEHARA INVENT ATTORNEYS METHOD AND APPARATUS FOR CHARGING STEEL SLABS INTO REHEATING FURNACE BACKGROUND OF THE INVENTION matic setting of pusher stroke in the steel slab reheating fur-' nace of Walking-beam type.

2. Description of the Prior Art The steel slab reheating furnaceof Walking-beam type generally has fixed and movable skids on its base, and is so constructed that the steel slabs charged into the furnace one after another are transferred on the fixed skids by the link movement of the movable skids.

In the furnace of this type, steel slabs are charged one after another at very short intervals and nearly in contact with each other, so that their expansion due to heat presses and tends to damage the skids. In order to avoid this-trouble, it might be better to maintain the interval between each two slabs constant. But it is difficult to set such intervals.

There is still another problem that too long an interval between two slabs reduces the efficiency of furnace operation. 7

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems by providing a method and control apparatus for charging steel slabs one after another into the reheating furnace of Walking-beam'type automatically at constant intervals.

Another object of the present invention is to provide a control apparatus for automatic setting of pusher stroke, which can easily be installed on the steel slabs reheating furnace of conventional Walking-beam type, which is free from cumulative errors possibly caused by the repetition of setting of pusher stroke, and which can be operated easily and accurately.

In order to perform theabove objects, the present invention is so constructed that the volume of pusher stroke SB used for the previously charged steel slab B is detected, then the distance DB of movement of said slab B by Walking-beam in the reheating furnace is measured, the sum of the measured width WA of the previously to-be-charged steel slab A and the prescribed interval between two steel slabs AW is subtracted from the sum of said distance DB and said volume of pusher stroke SB, and the value so obtained is transmitted to the pusher driver, thereby making it possible to charge steel slabs into the reheating furnace automatically at constant intervals.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is the longitudinal section of a typical model of the reheating furnace of Walking-beam type. FIG. 2 illustrates one example of the movement of a point on the upper surface of the movable skid in relation to the upper surface of the fixed skid in the furnace of FIG. 1. FIG. 3' is the cross section of the fixed and movable skids to show the relation in position of both skids in the furnace of FIG. 1. FIG. 4A, FIG. 4B and FlG. 4C respectively illustrate charging operations according to the present invention. FIG. 5 is the block'diagram showing one example of the operation of the control apparatus according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The support 4 of the movable skid 5 is fixed on the beam 7, which is driven horizontally and vertically by the oil hydraulic or electric driver 6 placed in the lower part of the base of the reheating furnace.

Across the reheating furnace are arranged several sets of each the fixed skids 3 and the movable skids 5; the link movement ofall the movable skids 5 is simultaneous.

FIG. 2 illustrates the movement of a point on the upper surface of the movable skid driven by the oil hydraulic or electric driver by the locus formed by said point and the horizontal straight line 11 showing the upper surface of the fixed skid 3.

By the link movement. that is, the cycle of moving upward, forward, downward and backward of the movable skid 5, the steel slab which has been charged on the fixed skid 3 by the pusher from the table roller 9, is held up, moved horizontally. and placed on the fixed skid 3. During this cycle, as it is moving horizontally, the tip of the charged steel slab is detected by the position detecter T using phototubes, etc. set at the outlet of the reheating furnace; this finding is immediately transmitted to the driver 6 to stop the slab at the prescribed position so that it is taken out of the furnace by the slab extractor 15 at desired time (determined according to the rolling schedule).

In the furnace of this type, steel slabs are charged nearly in contact with each other as mentioned above, therefore, their heat expansion gives stress to the skids and tends to damage them.

In view of these difficulties in the operation of the reheating furnace of Walking-beam type, the present invention is intended to determine the position for charging steel slabs, that is, the volume of pusher stroke by the very simple method. The special characteristic of the present invention is that when charging steel slabs by the pusher in the steel slab reheating furnace of Walking-beam type, the-volume of pusher stroke SA is calculated from the formula SA SB DB WA --AW where SB means the volume of pusher stroke used for charging the previously charged steel slab B; DB means the distance on which the steel slab B was moved by the Walking-beam during the time from the measurement of pusher stroke used for charging the steel slab B to the start of charging the next steel slab A; WA means the width of the to-be-charged steel slab A; and AW means the prescribed interval between each two steel slabs in the furnace; and the volume of push stroke SA so calculated is transmitted to the pusher driver.

The following is detailed explanation of the present invention using a desirable example shown in the drawings.

The situation of FIG. 4A is assumed to be such that the steel slab B has been charged into the furnace by the pusher stroke SB, with the prescribed interval AW between the steel slab B and the previously charged steel slab C, and, before taken out of the outlet, the steel slab (Z) is at a standstill below the position detecter T.

Upon receiving the instruction according to the rolling schedule, the slab extractor 15 starts operation to take the slab Z out of the furnace. When the steel slab Y is taken out following the steel slab Z, it often takes place that the length L left before the prescribed position below the position detecter T after a number of movements of the movable skid 5 by turning the greatest moving distance (the distance of one cycle movement) is short of one turn of the greatest moving distance of the moving skid 5. (See FIG. 4B). Hereafter, L also represents the charge adjusting distance of the moving skid 5. In order to move the steel slab Y as far as the prescribed position, the movable skid 5 is set in motion to start moving the steel slab Y, and when the tip of the steel slab Y reaches just below the detector T, this detecter issues the instruction to stop the driver 6 of the movable skid 5 so that the steel slab Y is stopped at the prescribed position (FIG. 4C).

Then, the steel slab A is charged into the furnace, when there exists the relation between the stroke SA of the pusher 8 for charging the steel slab A and the factors in charging the previously charged steel slab B, represented by the formula SA (SB DB) (WA AW), where DB means the distance WA means the width of the steel slab A, AW means the prescribed interval between the steel slab A and the steel slab B. Thus, the volume of pusher stroke for the to-be-charged steel slab can easily be calculated from the width of the previously charged steel slab, and the prescribed interval between each two steel slabs in the furnace, if the volume of pusher stroke for charging the previously charged steel slab SB and the distance on which this slab was transferred in the furnace are kept in memory.

H6. 5 illustrates one example of the application of the above gist of the present invention to the control apparatus.

Seventeen denotes the pusher controller for controlling the volume of stroke by the pusher 8 for charging steel slabs; 18 denotes the pusher strokedetecter attached to said controller 17 to detect the volume of pusher stroke to be controlled by the controller; 19 denotes the manual setter for determining the width of the to-be-charged steel slab; 20 denotes the manual setter for setting the prescribed interval between the rear tip of the previously charged steel slab and the front tip of theto-be-charged steel slab, 21 denotes the oil hydraulic or electric driver for driving the movable skid 5; l2 denotes the movable skid moving distance detecter'attached to the driver 21 to detect the distance of the horizontal, forward movement made during one cycle of the link movement of the movable skid 5 (during which the slab to move upward, horizontally forward, downward and horizontally backward) (every time after the'greatest horizontal movement has taken place, the detecter is reset); 13 denotes the detecter attached to the driver 21 to detect whether the greatest horizontal (forward) movement has been completed, and to issue a signal for every cycle; 14 denotes the counter for counting'signals issued byv the predetermined way to calculate the volume of pusher stroke SA, transmit the value so calculated to the pusher stroke controller 17 and reset the detecters 12 and 18 and the counter 14. v

The description of operation of the control apparatus, using the above-mentioned situation of FIG. 4, is:

The volume of pusher stroke SB of the previously charged steel slab is detected by the detecter 18 and memorized by the operation controller 16. When the to-be-charged steel slab A has reached the prescribed position on the table roller 9, a manual or timing signal is issued to have the operation controller 16 memorize the predetermined width WB of the steel slab and the prescribed interval between each two steel slabs AW, Also, in the operation controller 16, the number N of the greatest movements of the moving skid supplied from the counter 14 and the distance on which the movable skid was moved IM, supplied from the detecter 12 are read. DB is calculated from these data together with L, if necessary, to obtain finally the volume of pusher stroke SA necessary for moving the'to-be-charged steel slab A from the table roller to the fixed skid 3, using the relation formula SA=SB+ DB (WA AW), this value to be transmitted to the pusher stroke controller 17 automatically in the prescribed sequence.

Simultaneously, allhthe measured and. calculated values memorized by the operation controller-1'6 are canceled except for the volume of pusher stroke SA, and the detecters 18 and 12 and the counter 14 are reset upon receiving the signal of the completion of reading data from the operation controller 16. Thus, the volume of pusher stroke for the next to-becharged steel slab is determinedonly on the basis of factors concerning the previously charged: steel slab. According to the present invention, all the measured values except the volume of pusher stroke for the previously charged steel slab are canceled once this steel slab is charged, which adds to the present invention a great merit of the repetition of setting operation conditions being free from accumulative errors.

Even in such a special case where two or three steel slabs are taken .out from the furnace and one steel slab is charged instead, it is evident that the method of the present invention can be carried out without difficulty if [M, its number of movements, L, etc. of the taken out steel slabs are memorized by the pusher stroke controller.

We claim: 1 r

1. A method for charging steel slabs which comprises, when charging steel slabs by the pusher into the steel slab reheating furnace of the Walking-beam type which has fixed and mova ble skids and is constructed to have the charged steel slabs transferred by the movable skids, detecting the pusher stroke of the steel slab charged preceding a steel slab to be charged by means of a detector, making an operation controller memorize said detected pusher stroke, detecting the distance over which the previously charged slab is advanced by the movable skids and making said operation controller memorize said distance and also memorize the premeasured width of said steel slab to be charged and the preset interval between any two steel slabs by means of the signals from setters for setting said slab width and said slab interval, making said operationcontroller subtract the sum of said slab width and said slab interval from the sum of said pusherstroke and said slab advance distance, the resultant difference being the pusher stroke value for said steel slab to be charged, and transmitting the thus determined value through a pusher stroke controller to a pusher driver, whereby said slab travels the I determined stroke,

2. A control apparatus for controlling the charging of steel slabs in asteel slab reheating furnace of the Walking-beam type, having movable skids for transferring said slabs and a pusher for charging said slabs, said control apparatus comprising a first setter means mounted for-determining the width of the slab tobe-charged; a second setter means mounted for setting a preset interval between any two of'said steel s'labs in said furnace; a first detectoroperatively associated with said furnace for determining the volume of thepusher stroke of the previously charged steel slab; a counter mounted to count the number of movements of said movable skid; a'second detector operatively associated with said furnace for determining the distance of movement of said movable skid; an operation controller means adapted to receive the measurements from said first setter means, said second setter means, said first detector, said counter and said second detector for determining the volume of the pusher stroke volume necessary for said slab tobe-charged; a pusher stroke controller adapted to receive said pusher stroke volume for said slab to-be-charged from said operation controller means; and pusher driver means adapted to receive a command from said pusher stroke controller and operatively associated with said pusher to move said pusher to charge said slab to-becharged according to said command. 

1. A method for charging steel slabs which comprises, when charging steel slabs by the pusher into the steel slab reheating furnace of the Walking-beam type which has fixed and movable skids and is constructed to have the charged steel slabs transferred by the movable skids, detecting the pusher stroke of the steel slab charged preceding a steel slab to be charged by means of a detector, making an operation controller memorize said detected pusher stroke, detecting the distance over which the previously charged slab is advanced by the movable skids and making said operation controller memorize said distance and also memorize the premeasured width of said steel slab to be charged and the preset interval between any two steel slabs by means of the signals from setters for setting said slab width and said slab interval, making said operation controller subtract the sum of said slab width and said slab interval from the sum of said pusher stroke and said slab advance distance, the resultant difference being the pusher stroke value for said steel slab to be charged, and transmitting the thus determined value through a pusher stroke controller to a pusher driver, whereby said slab travels the determined stroke.
 2. A control apparatus for controlling the charging of steel slabs in a steel slab reheating furnace of the Walking-beam type having movable skids for transferring said slabs and a pusher for charging said slabs, said control apparatus comprising a first setter means mounted for determining the width of the slab to-be-charged; a second setter means mounted for setting a preset interval between any two of said steel slabs in said furnace; a first detector operatively associated with said furnace for determining the volume of the pusher stroke of the previously charged steel slab; a counter mounted to count the number of movements of said movable skid; a second detector operatively associated with said furnace for determining the distance of movement of said movable skid; an operation controller means adapted to receive the measurements from said first setter means, said second setter means, said first detector, said counter and said second detector for determining the volume of the pusher stroke volume necessary for said slab to-be-charged; a pusher stroke controller adapted to receive said pusher stroke volume for said slab to-be-charged from said operation controller means; and pusher driver means adapted to receive a command from said pusher stroke controller and operatively associated with said pusher to move said pusher to charge said slab to-be-charged according to said command. 